I was on another forum today and read a post from a guy who had just experienced something I have also seen. Apparently he had been using a cut-off disc on a 4 1/2" grinder and since the disc was already mounted on the grinder he attempted to grind a nub off of a spot weld with it and the disc disinterested. I myself have been guilty of doing this and also have experienced exploding discs which can be very dangerous, about 10 years ago in Ky a guy was very seriously injured when one exploded and hit him in the neck nearly killing him. Apparently these things are safe only for cutting with the edge and attempting to grind with one, even for only a very short time, is a very dangerous practice and should never be done. Personally I will never attempt it again since it takes only seconds to change to the right disc and the results from not doing so might be disastrous. Anyone else have thoughts on this?